A prior art ionic concentration measuring apparatus 65 is shown in FIG. 6A. The measuring apparatus has a body 62 with an operating display 61 on an exterior surface 80. A cylindrical member 64 is made integral at an end 82 of the body 62, and includes a measuring electrode 63.
FIG. 6B shows a prior art pocket-sized, substantially flat measuring device 69. The flat measuring device 69 includes a flat body 67 constructed similar to a card-type pocket calculator. The flat body 67 has an operating display 66 on a flat exterior surface 84. A flat surface sensor 68 is located on the body's surface 84.
Both prior art devices 65, 69 are manufactured by Horiba, Ltd., Japan, and are disclosed in pending Japanese Patent Application No. Sho 61-285371 and Japanese Patent Application Laid-Open No. Sho 63-138255.
A disadvantage of the immersion measuring apparatus 65 is that it is necessary for the cylindrical member 64 and the measuring electrode 63 to be immersed in the liquid to be tested 70. If there is not sufficient liquid to be tested 70 in order to fully immerse the measuring electrode 63, then the liquid 70 cannot be measured.
The flat measuring device 69 allows ionic concentrations to be measured by merely dropping a small quantity of liquid to be tested 70 onto the flat surface sensor 68 by a syringe 71. However, the flat device 69 must be placed on a substantially flat surface for the device 69 to operate properly. Further, the structure of the body 67 is not waterproof, and if the liquid to be tested 70 or other moisture is spilled on or around the body 67, water may enter the body 67, substantially affecting measurements being conducted.